I have a LG OLED 65C1, now rooted with RootMyTV v2. I have been hacking around exploring all the possibilities, and this gist is thus a personal cheatsheet.
If ever your TV goes into servicing at LG for whatever reason, it would be better to have every chances to your sides by not allowing them seeing you made some "not covered" stuff to the TV.
A reboot command can be detected, so there's an alternative. But it has to be confirmed yet if it's really stealth or not.
Please however note the following from @Informatic. But we don't know if LG can do something about it: